Venezuela’s sudden demand to renegotiate its billions in debt could complicate life for its two biggest oil patrons, China and Russia.

State-owned Petroleos de Venezuela SA, keeper of the world’s largest oil reserves, has seen output drop to a 14-year low, beset by the country’s economic collapse, a global plunge in crude prices and U.S. sanctions. As American refineries, once PDVSA’s top customers, have bought less, China and Russia have stepped in. The two countries have loaned more than $60 billion to boost production there, prepaying for more than a billion barrels.